Buzzer having convex thin film sounding member

ABSTRACT

A BUZZER DEVICE INCLUDING A VIBRATOR HAVING A MAGNET AND ELECTROMAGNETIC MEANS FOR EXCITING SAID VIBRATOR. THE BUZZER DEVICE FURTHER INCLUDES A VIBRATION FILM THAT IS STRUCK BY THE EXCITED VIBRATOR TO PRODUCE A RELATIVELY STRONG BUT PLEASANT SOUND.

1971 YUKIO ARAI 3,564,54

BUZZER HAVING CONVEX THIN FILM SOUNDING MEMBER Filed Feb. 11, 1969 2 Sheets-Sheet 1 FIG. 1

FIG. 2

U 7 u v: I u ll j l T R 16, 1 YUKIO ARAI 3,5645

I BUZZER HAVING CONVEX THIN FILM SOUNDING MEMBER Filed Feb. 11, 1969 ZSheets-Sheet 2 FIG.4 FIG. 5

' L2 ;,rL1o2 F v U I 1 5! L101 RIOO United States Patent 3,564,542 BUZZER HAVING CONVEX THIN FILM SOUNDING MEMBER Yukio Arai, Chiba, Japan, assignor to Kabushiki Kaisha Hattori Tokeiten, Tokyo, Japan Filed Feb. 11, 1969, Ser. No. 798,316 Claims priority, application Japan, Feb. 14, 1968, 43/ 9,052 Int. Cl. G08b 3/10 US. Cl. 340-384 9 Claims ABSTRACT OF THE DISCLOSURE A buzzer device including a vibrator having a magnet and electromagnetic means for exciting said vibrator. The buzzer device further includes a vibration film that is struck by the excited vibrator to produce a relatively strong but pleasant sound.

BACKGROUND OF THE INVENTION (1) Field of the invention The invention relates to a buzzer, in which a vibrator is excited by an electromagnet, and a vibration film is struck by the excited vibrator, thereby producing sound.

(2) Description of the prior art The conventional buzzer comprises a vibrating plate equipped with an iron lead, an electromagnet acting on said iron lead, and a mechanical switch consisting of a fixed contact and a movable contact mounted to said vibrating plate so as to turn on and off electric power to said electromagnet. This conventional buzzer produces sound by causing the iron lead of the vibrating plate to be vibrated and strike the iron core of the electromagnet. Accordingly, the sound produced thereby is relatively Weak. In other words, the efficiency of the sound volume is low with respect to the power consumed. Furthermore, the sound produced is not pleasant to the ear. Still further, both the fixed and movable contacts cause in themselves a considerable amount of abrasion since these contacts repeatedly strike each other when the device is actuated. As a result, the contacts tend to develop an undesirable space therebetween that hinders proper contact between them when the device is actuated. On the other hand, in some cases, the contacts become welded together due to the spark produced thereby.

SUMMARY OF THE INVENTION The present invention eliminates the foregoing disadvantages inherent in the conventional buzzer and provides a novel and improved buzzer device.

One of the features of this invention is to provide a buzzer device comprising a vibrator having a magnet, an electromagnetic means acting magnetically on said magnet to excite said vibrator, and a vibration film that is struck by the excited vibrator. Thus, said vibration film is continuously struck by the excited vibrator, thereby producing a suflicient amount of sound. In addition, the tone is soft and pleasant to hear. Hence, for example, this buzzer is ideal when used as the alarm device of an alarm clock. The vibration film is preferably of a plastic film made of polyethylene, polyester, polyurethane, polyacetal, or the like, or a metallic film made of aluminum foil, tin foil, or the like. The vibration film may be shaped into a pyramid such as a triangular pyramid, a quadrangular pyramid, a pentagonal pyramid, or a cone such as a circular cone, an elliptic cone, or a bowl.

Another feature of the present invention is to provide a buzzer device in which the electromagnetic means includes an iron core and an exciting circuit for producing a magnetic field adjacent the iron core, said exciting circuit including a direct current source, a pick-up coil which is mounted on the iron core and operated to produce an induced current by the vibration of said vibrator, an active element for amplifying the induced current produced in said pick-up coil, and an exciting coil which is mounted on the iron core and operated to produce a magnetic field adjacent the iron core upon receiving the amplified current.

It is an object of the present invention to provide an improved buzzer device.

It is another object of the present invention to provide a buzzer device that is rich in sound volume and pleasant in tone.

It is still another object of the present invention to provide a buzzer device having an improved durability.

Various further and more specific objects, features and advantages of the present invention will appear from the description given below, taken in connection with accompanying drawings illustrating by way of example pre ferred embodiments of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional front view of the buzzer device of the present invention;

FIG. 2 is a sectional view taken substantially along lines IIII of FIG. 1;

FIG. 3 is a perspective view showing a vibration film utilized in the buzzer device of the present invention;

FIG. 4 is a diagram showing an exciting circuit utiized in the buzzer device of the present invention;

FIG. 5 is a diagram showing a modified exciting circuit utilized in the buzzer device of the present inventlon;

FIG. 6 is a diagram showing another modified exciting circuit utilized in the buzzer device of the present invention;

FIG. 7 is a plan view showing a modified vibration film utilized in the buzzer device of the present invention;

FIG. 8 is a plan view showing another modified vibration film utilized in the buzzer device of the present lnvention; and

FIG. 9 is a plan view showing still another modified vibration film utilized in the buzzer device of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 through 3, a frame 2 made of a synthetic resin is mounted in a box-like case 1 made of brass and secured thereto by a plurality of screws 15, and a U-shaped iron core 3 made with a magnetic material is supported by the frame 2 in such a manner that two legs 4 of the iron core extend upwardly. A bobbin 5 on which a pick-up coil L and an exciting coil L which are utilized to excite the iron core 3, are doubly wound is mounted on one of the legs 4.

The frame 2 includes a wall 6 on one side, and two columns 7 on its other side. A supporting plate 9 having a narrow, relatively long hole 8 is mounted on the top of the wall 6 and the columns 7 by the use of a plurality of screws 24. One end of a vibrating plate 10 is secured to the supporting plate 9 by a screw 11.

The vibrating plate 10 is a long, slender plate made of carbon steel. A yoke plate 12 made of a magnetic material is secured to the bottom of the end portion of the vibrating plate with a plurality of rivets 13. Two spaced magnets 14 are mounted on the bottom of the yoke plate 12, in positions facing respective ones of the top faces of the legs 4 of the iron core 3. The vibrat- 3 ing plate is free to move in and out of the hole 8 of said supporting plate 9 during the vibration thereof.

A vibration film 16 made of polyethylene terephthalate film of 0.1 mm. thick is shaped into substantially a quadrangular pyramid, having a bent portion 17 and a flange 18 around the periphery thereof. This flange 18 of the vibration film 16 is mounted on top of the side walls of the case 1 and a lid 19 covers the case and sandwiches the flange 18 between the top of the walls of the case and the lid 19. The vertex 20 of the vibration film 1 is positioned near the upper surface of the end portion of the vibrating plate 10.

The lid 19 is secured to the case 1 by a pluralityof screws 21, and a resonant cavity 22 is formed between this lid and said vibration film 16. The lid 19' has formed in its upper surface an opening 23 which communicates with the resonant cavity 22.

An adapter plate 25 is inserted in the case 1 so that the plate 25 can be dismounted therefrom when desired (see FIG. 2). The exciting circuit for the iron core 3 is wired on the adapter plate in a printed form. A transistor T and a resistor R are mounted on the adapter plate within the frame 2.

The exciting circuit will be specifically explained by referring to FIG. 4. The collector of the transistor T is connected to the base of the transistor by way of the exciting coil L and resistor R. The point at which the exciting coil L is connected with the resistor R is also connected to a DC power source E, and the emitter of said transistor is connected to the positive pole of said power source via a switch S. Also, the base terminal of said transistor is connected to the emitter terminal by the pick-up coil L The operation of this buzzer will now be explained. When the switch S is closed, current flows in the base of the transistor T by way of the resistor R. This current is amplified by the transistor. The amplified current flows in the exciting coil L By this, a flux is produced in the iron core 3, which then attracts the magnets 14. When the magnets approach the iron core 3, the magnetic reluctance becomes small. As a result, the flux increases and thereby produces an induced current in the pick-up coil L The current produced in the pick-up coil L due to the approach of the magnets 14 is amplified by the transistor T and is supplied to the exciting coil L whereby the iron core 3 increases its fiux to attract the magnets 14. When the magnetic attracting force of the iron core 3 reaches equilibrium with the elastic dynamic stability of the vibrating plate 10, the strength of the flux in the iron core 3 ceases to change. As a result, the induced current ceases to flow in the pick-up coil L and current no longer flows in the exciting coil L As a result, the vibrating plate springs back toward the vibration film by virtue of its own elastic dynamic stability, thus striking the vibration film 15. As the vibrating plate 10 once again approaches the iron core 3 by virtue of the plates elastic dynamic stability after the striking action, the flux in the iron core 3 varies to once again induce a current in the pick-up coil L Thus, the same operation as described above is repeated. As is obvious from the description given above, a non-polar current is given to the exciting coil L According to the foregoing embodiment, the loudness measured was about 80 phons at a position 10 cm. distant from the buzzer when the dimensions of the buzzer was approximately 24 mm. x 16 mm. x 12 mm. and the power used was 10 mw. This shows that the ratio or efficiency of the sound volume versus the power used is markedly improved in comparison with the buzzer according to the prior art.

Alternative embodiments of the present invention will be explained below. FIG. 5 shows another example of the exciting circuit in which a polarized current is supplied to an exciting coil L mounted on an iron core 103. Specifically, the positive pole of a DC power source E is connected to the collector of a transistor T through a switch S and the negative pole of another DC power source E is connected to the collector of another transistor T through a switch S Both bases of the transistors T and T are connected to one end of a pick-up coil L and both emitters of said two transistors are connected to the other end of said pick-up coil L and to one end of the exciting coil L respectively. The other end of the exciting coil L is connected to the negative pole of the DC power source E and also to the positive pole of the DC power source E through a resistor R Assume that this exciting circuit is used for the buzzer shown in FIG. 1. Then, said transistors T and T amplify the induced current produced in the pick-up coil L during the times that the magnet approaches and moves back from the iron core 103. By this operation, a polarized current is supplied to the exciting coil L whereby the iron core 103 which is excited by the exciting coil L is operated positively to attract as well. as to reject said vibrating plate. As a result, it becomes possible to cause the vibration film to produce a greater striking sound.

FIG. 6 shows another example of the exciting circuit in which an AC power source E is connected to an exciting coil L mounted on an iron core 203. The iron core 203 to be excited by the exciting coil L is operated positively to attract as well as to reject said vibrating plate. The current supplied to the exciting coil L from said AC power source E should preferably be arranged to have the same frequency as the natural frequency of the vibrating plate. Thus the ratio or efliciency of the sound volume versus the power consumed thereby is increased.

FIG. 7 shows a vibration film 316 of cone shape having a vertex 320 in its center, a bent portion 317 around its circumference, and a flange 318 around the outer circumference.

FIG. 8 shows a vibration film 416 of elliptic cone shape having a vertex 420 in its eccentric position, a bent portion 417 around its circumference, and a flange 418 around the outer circumference.

FIG. 9 shows a vibration film 516 of bowl shape having a bent portion 517 around the circumference, and a flange 518 around the outer circumference.

What I claim and desire to secure by Letters Patent is:

1. A buzzer device comprising a striking member, means for vibrating the striking member, a vibration film having a thickness on the order of .1 mm., and including a convex portion thereon, and means for positioning said member so that said member strikes said vibration film at said convex portion as said member is vibrated to produce a relatively strong but pleasant sound.

2. A buzzer device as set forth in claim 1 wherein said vibration film is composed of a plastic.

3. A buzzer device as set forth in claim 1 wherein said vibration film is composed of a metal.

4. A buzzer device as set forth in claim 1 including a housing for said striking member and vibrating means and for supporting said film, and including a cover mounted on said housing in spaced relation with said film, and a resonant cavity having walls defined by said vibration film and cover.

5. A buzzer device as set forth in claim 1 wherein said means for vibrating said striking member includes electromagnetic means comprising an iron core and electric circuit means for producing a magnetic field in the vicinity of said iron core and wherein said striking member includes a springably mounted magnet aligned with said iron core and spaced from but placed sufficiently close to said iron core to be pulled towards said iron core when said electric circuit is energized to produce the magnetic field in the vicinity of said iron core.

6. A buzzer device as set forth in claim 5 wherein said electric circuit means includes a D.C. power source, a pick-up coil and an adjacent exciting coil mounted on said iron core, means for selectively connecting said D.C.

power source to said exciting coil to produce a varying magnetic field for inducing a current in said pick-up coil, amplifying means having an input lead connected to said pick-up coil, and having an output lead connected to said exciting coil, wherein the magnetic field produced in the vicinity of the iron core attracts said magnet causing the field to increase until further movement of the magnet is blocked, whereupon the field becomes constant and the induced current ceases, thereby decreasing the voltage applied to the exciting coil and releasingthe magnet to spring back.

7. A buzzer device as set forth in claim 6 wherein said electric circuit means includes means for positively moving said striking member towards and away from said vibration film.

8. A buzzer device as set forth in claim 7 wherein said electric circuit means includes an exciting coil and an adjacent pick-up coil mounted on said iron core and an 6 A.C. power source selectively connected to said exciting coil.

9. A buzzer device as set forth in claim 8 wherein said A.C. power source includes means for supplying a current to said exciting coil having the same frequency as the natural frequency of said vibrating striking member.

References Cited UNITED STATES PATENTS 1,942,811 1/1934 Green 340400 2,850,724 9/1958 Bassani 340392 2,946,995 7/1960 Gosswiller 340-400 3,127,602 3/1964 Russo 340392 HAROLD PITTS, Primary Examiner US. Cl. X.R, 

